The SABRE Lite is a low-cost development platform featuring the i.MX 6 Quad processor.
Development system-on-a-chip(SoC) platforms such as this are ideal for experimenting with kernels, operating systems and hardware.
The device features:
The Sabre Lite has been configured to load a first stage boot loader, U-Boot, from SPI flash memory. U-Boot is a popular open source boot loader that supports a wide range of features. Its primary role is to enable peripherals and secondary storage in order to load and boot a complete operating system from a variety storage media.
U-boot is highly configurable to suit the needs of the specific hardware platform and the application. The U-Boot provided with the COMP9242 kit has been configured to provide a richer set of features and an appropriate default environment for your project.
Once U-Boot has loaded, it will wait a few seconds before executing the default boot command. This is your chance to stop the boot process and enter the U-Boot prompt. Once at the U-Boot prompt, type help to view a list of commands or print to display a list of environment variables.
Key environment variables:
If in doubt, you can retore the default environment by typing run clearenv.
Key U-Boot commands:
Once you have finished, you can resume the auto boot process by running run bootcmd
The kit given out for COMP9242 contains the following items:
The CSE lab machines already have the required software installed. See milestone 0 for details.
Your host machine will require certain software and drivers to talk to the Sabre. This is mostly machine specific:
Use the USB-serial and serial cables to connect the Sabre Lite serial port marked debug to your host computer. This will allow us to see output and debug the device over serial.
You will also need a network connection between the host computer and the Sabre Lite for downloading OS images, communicating with NFS file systems and to provide a console over LAN. If you are in a CSE lab or do not have a spare Ethernet port, you will need to use the provided USB/Ethernet dongle. Connect the Ethernet cable cable from the Sabre Lite to the USB/Ethernet dongle and then connect the dongle to your computer.
Once the Sabre Lite is connected to your development machine you should
launch the two consoles that connect you to its output. Run
minicom in one console window and
nc -lup 26706
in the other.
You may be required to change the settings for minicom. On linux, use
dmesg to work out which port the USB to serial converter has
been attached to (its usually
/dev/ttyUSB0). Then set minicom
to use that serial port, 115200 baud rate, 8N1, and no hardware flow
sudo minicom -s /dev/ttyUSB0.
Plug in the power cable for the Sabre Lite or press the reset button on the top of the Sabre Lite to reboot. When minicom is connected to the serial port, you should see some output from U-Boot in the minicom window.
A brief description of the development cycle can be found in Milestone 0. A lot is happening under the covers to allow you to easily develop an operating system:
On CSE machines this generates a hotplug event on the host's USB bus and results in the creation of the tty device. A cse script runs at this time and customises the tftpd and nfs server to your login sessions user name.
When minicom launches it opens the tty device.
Not magical, nothing will happen though until you send something with libserial.
A lot is happening here under the covers, the Makefile will first build your OS, generating a boot image bootimg.elf. Once the build is complete, make copies the images/sos-image-arm-imx6 file to your tftpboot directory. Then, a reset signal is sent over serial, which causes the kernel to reboot the device. When the device reboots, tftp will fetch the newly built image over tftp and execute the image.
Are you wondering why you started this course now? Just think how good it will feel when you finish!
An installation of Ubuntu Linux has been supplied on the given µSD card. To boot this image, you will need to interrupt the default boot process.
First reset your Sabre Lite by pressing the button on top of the box.
Next wait for
Hit any key to stop autoboot: to appear and
press a key in the minicom window to stop the automatic boot process.
U-Boot 2013.04-dirty (Jul 21 2013 - 23:42:37) CPU: Freescale i.MX6Q rev1.2 at 792 MHz Reset cause: POR Board: MX6Q-Sabre Lite DRAM: 1 GiB MMC: FSL_SDHC: 0, FSL_SDHC: 1 SF: Detected SST25VF016B with page size 4 KiB, total 2 MiB *** Warning - bad CRC, using default environment No panel detected: default to HDMI unsupported panel HDMI In: serial Out: serial Err: serial Net: using phy at 6 FEC [PRIME] Warning: FEC using MAC address from net device Hit any key to stop autoboot: 2
Finally, run the pre-defined boot script by entering
When prompted for a user name, enter
ubuntu. The password is